Young children, I think, before they really achieve a sense of awareness, usually live right for the moment. It's a very innocent way of life. Once we achieve self-awareness and, particularly, a sense of our own mortality, we really begin to be aware of our choices.
The medieval years saw people definitely act through a sense of fear; a fear of eternal damnation. And we definitely see fear at play today: fear of "other people" (I call that "Fear of The Other"), fear of losing a job, fear of war, etc. It's a great motivator for those who know how to manipulate it.
On a more personal level I think the people that I admire the most are those who do not have a fear of failing, which has always been my most damning demon. Stepping out of one's comfort zone is what makes a person great.
I'm personally still looking for "that thing," or purpose. I know what I'd prefer to do, but not sure it's a purpose. If I ever find it I'll let you know.
Thanks for the thoughtful post!